Question

1. Why chemical reactions are in accordance with the law of conservation of mass?

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2.Calculate the ratio of atoms present in 5g of magnesium and 5g of iron.

Answer 1

1) Chemical reactions follow the law of conservation of mass because the reactants and products are chemical substances which are basically nothing but matter, and by the law of conservation of mass matter can neither be created nor be destroyed. Therefore chemical reaction follow the law of conservation of mass.

2) The molar mass of magnesium is 24 g. We know that one mole of a substance contains 6.023 X 10²³ particles. Therefore

number of atoms present in 24g of Mg = 6.023 X 10²³

number of atoms present in 1 g of Mg = (6.023 X 10²³) / 24

number of atoms present in 5g of Mg = (6.023 X 10²³ X 5) / 24

= 12.547 X 10²²

The molar mass of iron is 56g. Therefore

number of atoms present in 56g of Fe = 6.023 X 10²³

number of atoms present in 1 g of Fe = (6.023 X 10²³) / 56

umber of atoms present in 5g of Fe = (6.023 X 10²³ X 5) / 56

= 5.377 X 10²²

So, the ratio of atoms in 5g of Mg and 5g of Fe is

= 12.547 X 10²² / 5.377 X 10²²

= 2.333